Apparatus for mixing of liquids at an adjustable ratio

ABSTRACT

Arrangement for mixing of liquids at an adjustable ratio of mixing comprising a number of plates with at least one internal longitudinal cut, the plates being piled one on another, a stable separating wall engaging into said cuts allowing a relative sliding movement of the plates so as to adjust the ratio of the spaces defined by the longitudinal cuts of the plates in front of and behind the separating wall, which spaces being adapted to contain liquids of different densities.

States 1191 1111 3,863,901 Janda et al. Feb. 4, 1975 APPARATUS FOR MIXING 0F LIQUIDS AT 3,214,144 10/1965 Gugel 259/7 AN ADJUSTABLE RATIO 34243463 3/1966 3,549,131 12/1970 Inventors: Ivan Janda; Miro a Berta, both of 3,753,554 8/1973 MOllCI 259/8 Prague, Czechoslovakia [73] Asslgneez g sgszfgggzigsgjg fg Primary Examiner-Robert W. Jenkins [22] Filed: Oct. 15, 1973 [21] Appl. No.: 406,670 [57] ABSTRACT Foreign Application Priority Data Arrangement for mixing of liquids at an adjustable Oct. 13, 1972 Czechoslovakia 6912-72 ratio of mixing comprising a number of plates with at least one internal longitudinal cut, the plates being [52] U.S. Cl. 259/7 piled one on another, a stable separating wall engaging [51] Int. Cl B0lf 7/24 into said cuts allowing a relative sliding movement of [58] Field of Search 259/4, 7, 8, 5, 6, 22, the plates so as to adjust the ratio of the spaces de- 259/23, 24, 40, 41, 42, 43, 44 fined by the longitudinal cuts of the plates in front of V and behind the separating wall, which spaces being [56] References Cited adapted to contain liquids of different densities.

UNITED STATES PATENTS 3,123,342 3/1964 Little 259/8 3 Claims, 10 Drawing Figures PATENTED 3.863.901

SHEET 2 OF 4 APPARATUS FOR MIXING OF LIQUIDS AT AN ADJUSTABLE RATIO BACKGROUND OF THE INVENTION This invention relates to an apparatus for mixing of liquids at an adjustable ratio of mixing, i.e., an arrangement for the preparation of concentration gradients for liquids according to instantaneous requirements. The mixing of liquids at a ratio variable with time is frequently used in centrifuging, for chromatographic elution (gradient of polarity, ion force, or pH), electrophoresis and isoelectric focussing.

Apparatus which is actually used for the preparation of gradients either produce gradients of a single type only, which are determined by the design of the apparatus and do not permit the alteration of the concentration of the discharged mixture according to the requirements of a predetermined program of gradients, the apparatus adopted for general use is complicated and is therefore quite expensive. In addition, prior available apparatus of reasonable cost, which does not use electronic regulation of the mixing ratio to calculate the shape of the produced gradients from the shape of the different elements of the respective apparatus. An automatic calculator was necessary to arrive at the shape of an apparatus producing a required gradient having a common program.

SUMMARY OF THE INVENTION It is an object of this invention to provide a very simple and cheap apparatus which permits the mixing of liquids at continuously variable mixing ratios. The apparatus according to this invention comprises a number of horizontally arranged plates with cuts, said plates being mutually slidably piled on a base plate having a vertical partition wall. Such wall divides the internal space of the cuts of these plates to two chambers so that the sum of the thus defined spaces of these chambers, depending on the position of the plate with respect to the partition wall, is constant at every height. Discharge ports are provided in the base plate, said ports being connected with a device for equalizing the levels of the liquids in the chambers and for mixing these liquids. The base plate can be provided with means for adjusting the plates to the required positions and for their pressing against the base plate in order to prevent leakage of liquids from the chambers through gaps between the plates.

The device for equalizing the level of the liquids in the chambers and for mixing these liquids can be advantageously a vessel with an agitator, said vessel having a discharge port in the bottom and supply ports in the side wall at the same level. Such supply ports are connected by flexible hoses with the discharge ports of the chambers, whereby the body comprising the system of plates on the base plate with the partition wall and the fixing means is firmly connected to a lifting device, thereby permitting the body with the plates to be raised with respect to a stable equalizing and mixing device.

The arrangement according to this invention is practically suitable for general use despite its maximum simplicity and low cost. It permits a linear transformation of the shape ofa required concentration gradients to be made in order to obtain the correct shape of the chambers shifting the plates.

DESCRIPTION OF THE DRAWINGS A preferred embodiment of an arrangement for the mixing of liquids at an adjustable mixing ratio is shown in the attached drawings, where:

FIG. 1 is a view partly in elevation and partly in section of the assembled body of the arrangement, the section being taken through the centers of the face walls of the plates;

FIG. 2 is a top view thereof;

FIG. 3 is an elevation of the assembled body of the arrangement in section taken along a plane indicated in FIG. 2 by the line AA, showing simultaneously the operation of the device for equalizing the level and mixing of liquids in the course of emptying the chambers;

FIG. 4 is a cross sectional view of another device for equalizing the level and for mixing the liquids;

FIGS. 5, 5a 5d, respectively, are top views of different alternative embodiments of plates;

FIG. 6 is an example of the program of a predetermined gradient; and

FIG. 7 shows the transformation of the program of this gradient for application for an arrangement according. to this invention.

FIG. 1 together with FIG. 3 serve for an explanation of the principle of the operation of the apparatus of the invention.

The symbols used on the drawings have the following meaning:

h distance from the initial level of the liquids in the chambers indicated in FIG. 1 by a broken line.

u(h) distance of the face ofa plate from the partition wall as a function of h.

(The diagram u(h) in dependence on h thus forms the circumferential curve determining how the plates should be assembled in an elevational view).

c, concentration of the solution in the first chamber 0 concentration of the solution in the second chamber c(h) concentration of the solution discharged from the mixing device in dependence on the instantaneous level of the solutions in the chambers.

P,(h) cross-section of the first chamber 011 dependence on h.

P h) cross-section of the second chamber in dependence on h.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, chambers l and 2 are provided for mixing of liquids, said chambers being formed by main longitudinal cuts in horizontal plates 3. Plates 3 are piled one on another and are adjusted on a base plate 4 which is provided at its center with a vertical partition wall 5 fitting closely, but in sliding fashion, to the planar internal walls of the main longitudinal cuts of-the plates 3 so, that the plates 3 can be assembled to a suitable body while preventing leakage of liquids be tween chambers 1 and 2. Discharge ports 6 are provided in the base plate 4 at both sides of the partition wall 5, ports 6 being connected by flexible hoses 7 with a device 8a d for equalizing the level of the liquids in the chambers l and 2 and for mixing these liquids. In the embodiment shown in FIG. 3, the mixing and equalizing of the levels of the liquids is performed in a single mixing chamber 8a with two supply ports 8b at the same level, with a discharge ports 80 in the bottom part of the mixing chamber 8a and with an agitator, for instance, a mixing screw 8d driven by a motor (not shown). It is of course also possible to separate in space the mixing device from the device for equalizing the level of liquids and to equalize the level by some other device, for instance, by means of floats and the like. The plates 3 are adjusted by the aid of fastening means 9a c, the function of which is to fix the plates in a certain position and to prevent leakage of liquids from the chamber 1, 2 via gaps between the plates 3.

As shown in FIG. 2, the plates 3 are provided at each side of the main cut with parallel cuts, through which parallel cuts there pass fastening bolts 9a, anchored in the base plate 4. A fastening plate 9b stiffer material but of the same shape as the other plates 3 is piled on top of all plates 3, thus distributing the pressure generated by wing nuts 90 over the whole surface of the plates 3. It is of course possible to use plates of other shape, as for the simultaneous preparation of more gradients of the same shape.

Some alternative examples of plates are shown in FIGS. 5a to 5d, which illustrate alternative arrangements of the supporting plate 4, of the partition wall 5, of discharge ports 6 and of fastening means 9; these illustrate the possible use of a plurality of equalizing and mixing devices 8. The plates 3 according to FIGS. 5a and 5b are shaped so as to reduce the torsional stress of the partition wall 5. In FIGS. 5c and 5d plates are shown for the simultaneous preparation of several concentration gradients of the same type. The fastening means can be also formed by vertical guiding ledges at both sides of the base plate 4 with plates 3. The ledges can be connected above the body of the plates to form yokes with threaded openings provided in the horizontal arms of these yokes for threaded pressure bolts generating on the plates 3 pressure from the top. In that case, no cuts for fastening means are required in the plates 3. The emptying of the liquid from the chambers 1, 2 is achieved by raising the body with the plates, which is for this purpose supported on a pantograph table (not shown). This raising of said body can of course be achieved in any other feasible manner. In FIG. 3 the direction of raising is indicated by an arrow. The table can be of course also raised manually or by means of a small motor acting through a gear transmission.

The described apparatus operates as follows:

The simple equation for masses holds true for the masses of solutions discharged from chambers 1, 2 within a short time interval Ar Am Am Am or c(h) S-Ah c, P,(h) Ah c P (h) Ah,

where c(h) is the concentration of the mixture discharged from the device 8 at the moment the levels of liquids in the chambers are at the height h, where P,(h) and P (h) are the cross sections of chambers l or 2 respectively at the height h, and the sum S of the cross sections of chambers l, 2 is constant,

S P,(h) P (h) const.

0, and c are concentrations of the solutions in chambers 1 and 2, Ah is the drop of the levels within the time From that follows that 20 2 l 0 CI] The required concentration gradient is, however, stipulated as a function of the height I of the level in the receiving vessel i.e. as G(1). However, as at each moment Sh P! where P is the cross section of the receiving vessel, the transformation (7(1) to G(h) 0!) can be easily accomplished by means of l S/p.h.

The transformation is either achieved directly by this substitution for the gradient G(I) stipulated as an analytical function or numerically, i.e., point by point for a gradient of common shape. For practical purposes it is advantageous to transform the dependence P (h) to u(h) indicating the dependence of the distance of the faces of the plates 3 from the partition wall 5. If we assume the shape of the plates 3 to be as in either one of FIGS. 1 and 5 with milled cuts where part of the surface P (h) is a semicircle of a radius r, the center of which is at the distance 2 from the near face wall of the plate. then h(h) z wr/4 S/Zr UI) 1/ 2 '1 EXAMPLE A concentration gradient of saccharose for centrifuging was obtained, determined by the function C(l) =5 l5( V l l/,) (see FIG. 6)

where G(l) is the concentration of saccharose at the distance 1 from the bottom of a cylindrical measuring cell having a cross section P= 300 mm indicated in percentage. L 50 mm is the maximum value of l. The measuring cell has the following parameters:

S 200 mm r= 2 mm, z =15 mm. Assuming c 3% and c 25%, we can evaluate by using the above equation.

u(h) 13.43 2.27 (2 +15 1 0,013 h) mm The values u(h) are plotted in a diagram in dependence on h (FIG. 7).

The plates 3 were put on the supporting plate 4 with the partition wall 5, and the diagram u(h) in dependence on h (FIG. 7) was placed to the not yet adjusted body of the plates 3 so that the direction of the axis h coincides with the right border of the partition wall 5 whereby the base plate 4 crosses the axis h at the place of the maximum value of h (in the present case h mm). The plates 3 were shifted so that their right faces just touch the curve of the diagram u(h) in dependence on h, that is that this diagram forms the circumferential curve of the body. The plates 3 were thereafter fixed by tightening the fastening wing nuts 9c against the top plate 9b. The assembled body was fixed to a lifting table, which was lowered so that the supply ports 8d were at the level of the starting level of liquids in the chambers l, 2 (in the present case 75 mm above the base plate 4). The hoses 7 connected to the supply ports 8b were connected to the discharge ports 6 of the chambers 1,2 and solutions of saccharose of a concentration c 3% and c 25% were poured into the chambers l and 2 up to the height determined by the height of the supply ports 8b. Now the motor of the mixing screw 8d was started and the body with the filled chambers l, 2 was raised with respect to the mixing device 8a d. The couple of vessels was thereby emptied into the mixing chamber 80, the solutions having concentrations c and were here perfectly mixed so that a mixture of the required concentration c(h) variable in dependence on the distance I from the bottom of the measuring cell (see FIG. 6) was discharged into the measuring cell situated below the discharge port 80.

The arrangement according to this invention can be applied for the preparation of concentration gradients for centrifuging in zonal rotors. Here the cylindrical rotor is rotating at high speed, so that the liquid fills it from the mantle toward the axis.

If the rotor has a radius R, a height v and the distance of the cylindrical level from the rotor mantle at some time t is equal to then 1r R v rrp v Sh where p R 11'. It is therefore necessary to use for transformation of the gradient which is stipulated as G (p) to the function C(h) the equation Although the invention is illustrated and described with reference to a plurality of preferred embodiments thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a plurality of preferred embodiments, but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

1. Apparatus for mixing liquids at an adjustable mixing ratio comprising;

a horizontal base plate,

a number of similar horizontally arranged plates with longitudinal cuts,

a vertical partition wall fixed to the base plate, the width of said partition wall being equal to the width of the longitudinal cuts in the plates,

the plates being piled on said base plate with the partition wall engaging into their longitudinal cuts,

the partition wall defining with each plate two separate spaces, the sum of the volumes of both said spaces being constant for each plate without regard to the position of the plate with respect to the partition wall,

fastening means for fixing the plates on the base plate in a predetermined relative position with respect to the partition wall,

the spaces of the piled up plates forming a chamber at each side of the partition wall, discharge ports in the base plate at each side of the partition wall for discharging liquid from both of said chambers, and for mixing these liquids, said device being connected with the chambers,

means for adjustment of the height of the composite body comprising the base plate, the plates and the partition wall with respect to the device for equalizing the level of liquids in both chambers and for mixing these liquids.

2. Apparatus according to claim 1, wherein the device for equalizing the level of liquid in both chambers is connected to the discharge ports of the chambers by flexible hoses.

3. Apparatus according to claim 2, wherein the device for equalizing the level of liquids in both chambers and for mixing these liquids comprises:

a vessel with agitator means,

the bottom of the vessel provided with said discharge openings supply ports provided in the vessel at the same level,

and further flexible hoses connecting the supply ports with discharge ports for discharging liquids from both chambers formed by the piled-up plates. 

1. Apparatus for mixing liquids at an adjustable mixing ratio comprising; a horizontal base plate, a number of similar horizontally arranged plates with longitudinal cuts, a vertical partition wall fixed to the base plate, the width of said partition wall being equal to the width of the longitudinal cuts in the plates, the plates being piled on said base plate with the partition wall engaging into their longitudinal cuts, the partition wall defining with each plate two separate spaces, the sum of the volumes of both said spaces being constant for each plate without regard to the position of the plate with respect to the partition wall, fastening means for fixing the plates on the base plate in a predetermined relative position with respect to the partition wall, the spaces of the piled up plates forming a chamber at each side of the partition wall, discharge ports in the base plate at each side of the partition wall for discharging liquid from both of said chambers, and for mixing these liquids, said device being connected with the chambers, means for adjustment of the height of the composite body comprising the base plate, the plates and the partition wall with respect to the device for equalizing the level of liquids in both chambers and for mixing these liquids.
 2. Apparatus according to claim 1, wherein the device for equalizing the level of liquid in both chambers is connected to the discharge ports of the chambers by flexible hoses.
 3. Apparatus according to claim 2, wherein the device for equalizing the level of liquids in both chambers and for mixing these liquids comprises: a vessel with agitator means, the bottom of the vessel provided with said discharge openings supply ports provided in the vessel at the same level, and further flexible hoses connecting the supply ports with discharge ports for discharging liquids from both chambers formed by the piled-up plates. 